I know you said you had your heat pump checked. Was it buy an Hvac tech??
I have been on many calls for high electric bills and found the heat pump only working off of the electric elements. Just my 2 cents that;s where I would start.

Are you turning your heat down and then back up often? Sometimes it's cheaper NOT to setback a heatpump in cold weather because increasing the temperature more than 3-5 degrees causes the backup electric elements to do the heating instead of the heat pump.

Set at a constant toasty 66 degrees during the day and . . .

Set at a constant toasty 66 degrees during the day and 64 degrees at night . . even on weekends. The kids aren't too thrilled but I can't imagine what the KWH usage would be if I kept it at 70 degrees.

I know this sounds incredibly stupid, but are the heat pump filters clean? There may be more than one set. Is the airflow out of the ducts the same as always? Reduced airflow will have very little effect on energy consumption of a gas or electric strip heat system, but will cause a heat pump to run alot more.

Any possibility that the crawlspace or attic access was left open? Maybe even a window? If you have access to the heating ducts, turn the fan on and look for leaks. This includes the return air duct, if it's in an unheated space.

This may be somewhat uncomfortable, but if you read the meter at a specific time one day, and read it again at the same time the next day, then turn the heat pump off for the next whole day, and read the meter at the specific time, you'll know just how much it's using.

To check for hot water leaks, don't use any hot water for a few hours, then feel the pipe on the cold side of the water heater, about 6" from the tank. It should be warm. If it isn't, you very likely have a leak.

Have any male adolescent(s) started taking abnormally long showers on a regular basis? Have you replaced any shower heads with water wasting full flow types? Has anyone new moved in? Has the utility replaced your meter with a more accurate one when possibly your prior meter was actually defective?

Nothing has changed except that several months ago (right before this problem started) I had the panel replaced and service upgraded. I can't remember now whether they also replaced the meter at that time; it has been replaced since I moved in but I can't remember now exactly when.

To work this is piecemeal and tedious but it may give you some idea if your house is an 'outlier.' Post what you know of your house, its size, your occupancy, your appliances, your climate and how your neighbors are doing.

Or if your local PoCo is in a good mood they may help you but they have their own biases.

Look, stating NOW that right before the problem started you had a panel change and new service is rather signifigant and should have been "mentioned." That oftentimes entails a new meter because upgraded meter pans can accept the newer, RF meters because it has a 5-jaw meter plug. This points toward you original meter was NOT functioning properly and was grossly under registering your usage and that the current readings are correct, OR the old meter was more accurate and your new meter is over-registering your usage. Since you heat with a heat pump realize this: The electric elements kick in when the temperature difference between setpoint and actual varies by 5 degrees or more, and that heatpumps are extremely expensive to operate in higher Kwh areas, and that they're more expensive to run in colder climates. In addition, it's possible your utility has changed you to a time of use plan or some other billing plan when your old meter was swapped out for the new. How has your billed usage changed since this first became a problem? Understand that heat pumps, though efficient in and of themselves, cost way more to operate than a gas or oil fired heating system, and builders usually go with them so they have only one system to install that covers air-conditioning and heat. They profit more that way but leave the homeowner to deal with crushing winter time electric bills in the future. A nearby condo development of extremely high-end waterfront condos initially installed heat pumps in the late 1980's and every single owner has since replaced them with gas fired heating systems at great expense.

hi, years ago I worked for an electric utility in cust. serv. at that time meters were mechanical and they were changed out every so many years and calibrated. the old mech meters did slow down over time, but never speed up.

with the upgrade and new meter you may have replaced an old, slow meter with a new calibrated one. to you that appears to be an increase in use, but really is an accurate meter showing true use.

ask the poco to do a meter test on your current meter.

by the way this thread is several years old. starting a new one next time might be in order.